Use pyrepl+fanycompleter as the default readline for pdb

Feature or enhancement

Proposal:

Once https://github.com/python/cpython/pull/130473 is merged, we can think of using it also for pdb.
This would enable colored completion from the pdb prompt, like this (for context, pdb++ has been doing this for years)

This raises some minor questions such as whether the (pdb) prompt should be white or magenta.

Has this already been discussed elsewhere?

No response given

Links to previous discussion of this feature:

No response

Linked PRs

• gh-141619

先閱讀 PR 130473 中引用的 pyrepl 和 fanycompleter 工作，然後檢查 pdb 如何選擇其 readline 實作以及如何處理 (pdb) 提示字元。當 pdb 預設使用 pyrepl+fanycompleter 並提供彩色補全時，此變更即完成；提示字元色彩的選擇仍需解決。PR 141619 表明這項工作已經在進行中。